Recently a shelf-stable, fast-curing, one component, alkoxy-functional room temperature vulcanizable (RTV) composition was disclosed in the patent of White et al., U.S. Pat. No. 4,395,526, and assigned to the same assignee as the present invention. Basically, White et al. disclose that moisture curable polyalkoxy-terminated organopolysiloxane RTV compositions can be made by combining (1) a silanol-terminated polydiorganosiloxane base polymer; (2) a crosslinking silane; (3) an effective amount of certain silane scavengers for chemically combined hydroxy radicals; and, (4) an effective amount of a condensation catalyst. The scavenger, which can be either a separate compound or part of the alkoxy-functional crosslinking agent, has a functionality selected from the group consisting of oximato, carbamato, enoxy, amino, amido, imidato, ureido, isocyanato and thioisocyanato. The disclosure of White et al. is incorporated by reference into the present application.
Other scavenger compositions that can be utilized in the White et al. one component alkoxy-functional RTV composition are disclosed in copending patent application by R. T. Swiger and J. E. Hallgren, Ser. No. 476,000, filed Mar. 17, 1983; J. J. Dziark, Ser. No. 349,695, filed Feb. 17, 1982; G. M. Lucas, Ser. No. 464,443, filed Feb. 7, 1983; Chung et al., Ser. No. 428,038, filed Sept. 29, 1982; Chung, Ser. No. 338,518, filed Jan. 11, 1982; and T. D. Mitchell, Ser. No. 462,949, filed about Feb. 1, 1983. All of the foregoing patent applications are assigned to the same assignee as the present invention and are also incorporated by reference into the instant disclosure. The reader is also referred to Ser. No. 487,778, Chung and Lucas, filed concurrently herewith and assigned to the same assignee as the present invention.
White et al. teach the artisan that a scavenger having the general formula: ##STR1## where R.sup.1 is an aliphatic organic radical having from 1 to about 8 carbon atoms and which is selected from the group consisting of alkyl radicals, alkylether radicals, alkylester radicals, alkylketone radicals and alkylcyano radicals or an aralkyl radical having 7 to 13 carbon atoms, R.sup.2 is a monovalent organic radical having 1 to 13 carbon atoms, and X is a hydrolyzable leaving group selected from the group consisting of amido, amino, carbamato, enoxy, imidato, isocyanato, oximato, thioisocyanato and ureido radicals; when combined with a diorganopolysiloxane base polymer, an effective amount of condensation catalyst and, when the hydrolyzable leaving group is enoxy, a curing accelerator, will provide a one package, stable, moisture curable RTV composition. White et al. teach further that the preferred R.sup.2 is selected from the group consisting of methyl, phenyl and vinyl, most preferably is methyl or a mixture of a major amount of methyl and a minor amount of phenyl and/or vinyl, and that the preferred X groups are amido, amino and enoxy, the most preferred being amido.
One shortcoming of a preferred embodiment of White et al., i.e. where R.sup.2 is methyl and X is enoxy, is that it produces translucent grades of RTV's that cure yellow in color. For marketing and aesthetic reasons it is highly desirable that the cured RTV composition be colorless.
It is therefore an object of the present invention to provide one package, stable, moisture curable organopolysiloxane compositions which produce translucent and colorless compositions upon curing.
Other objects and advantages of the present invention will be obvious from the following detailed description.